KR101273767B1 - Organic electroluminescent element and organic electroluminescent display device - Google Patents

Abstract

The present invention relates to a negative electrode, anode; A plurality of light emitting units stacked between the cathode and the anode via an intermediate unit; A cavity adjusting layer provided between the light emitting unit closest to the anode and the anode; And an electron extracting layer provided on the light emitting unit side adjacent to the cavity adjusting layer, and by adjusting the film thickness of the cavity adjusting layer, the optical distance from the light emitting position of each light emitting unit to the anode is adjusted. It relates to an electroluminescent element.

Organic electroluminescent element, light emitting unit, cavity adjusting layer, electron withdrawing layer

Description

Organic electroluminescent element and organic electroluminescent display device {ORGANIC ELECTROLUMINESCENT ELEMENT AND ORGANIC ELECTROLUMINESCENT DISPLAY DEVICE}

1 is a schematic cross-sectional view showing an organic EL device of an embodiment according to a first aspect of the present invention.

2 is a view showing the relationship between the driving time and the light emission intensity of the embodiment and the reference example according to the first aspect of the present invention.

3 is a diagram showing the relationship between the film thickness of the cavity adjustment layer and the driving voltage.

4 is a diagram showing an organic EL display device of one embodiment according to the first aspect of the present invention.

5 is a schematic diagram showing energy levels of LUMO and HOMO of each layer constituting the intermediate unit and the cavity adjusting unit in one embodiment according to the second aspect of the present invention.

6 is a cross-sectional view showing a bottom emission type organic EL display device of the embodiment according to the second aspect of the present invention.

Fig. 7 is a cross-sectional view showing a top emission type organic EL display device of the embodiment according to the second aspect of the present invention.

8 is a schematic view for explaining the effect of the third aspect of the present invention.

9 is a schematic cross-sectional view showing an organic EL device of an embodiment according to a third aspect of the present invention.

Fig. 10 is a diagram showing the emission spectrum in the front direction and the emission spectrum in the viewing angle of 60 ° in the organic EL device of the embodiment according to the third aspect of the present invention.

11 is a schematic cross-sectional view showing an organic EL device of Comparative Example 7. FIG.

It is a figure which shows the emission spectrum of the front direction of the organic electroluminescent element of the comparative example 7, and the emission spectrum of the viewing angle of 60 degrees.

<Code description>

1: anode

2: hole injection layer

3: cavity adjustment layer

4: electron withdrawing layer

5: first light emitting unit

6: intermediate unit

7: second light emitting unit

8: electron transport layer

9: electron injection layer

10: cathode

21: intermediate unit

22: cavity adjustment unit

23: first electron withdrawing layer

24: electron injection layer

25: first cavity adjustment layer

26: second electron withdrawing layer

27: electron supply layer

28: electron transport layer

50: first light emitting layer

5Oa: Light emitting position of the first light emitting layer

51: orange light emitting layer

52: blue light emitting layer

60: second light emitting layer

60a: light emission position of the second light emitting layer

61: orange light emitting layer

62: blue light emitting layer

70: intermediate unit

71: electron transport layer

72: electron injection layer

73: electron withdrawing layer

80: reflective electrode

81: metal thin film

81a: reflective surface of the reflective electrode

82: transparent conductive film

91: the first cavity adjustment layer

92: second cavity adjustment layer

93: electron transport layer

94: metal thin film electrode

101: light source (light emitting position of the first light emitting layer)

102: light source (light emitting position of second light emitting layer)

103: reflective surface of the reflective electrode

[Document 1] Japanese Unexamined Patent Publication No. 2003-272860

[Document 2] Japanese Unexamined Patent Publication No. 2004-342614

[Document 3] Japanese Unexamined Patent Publication No. 2003-151776

[Document 4] Japanese Unexamined Patent Publication No. 2004-207000

[Document 5] Japanese Unexamined Patent Publication No. 2003-229269

[Document 6] Japanese Unexamined Patent Publication No. 2006-49396

[Document 7] Japanese Unexamined Patent Publication No. 2003-272860

SYNTHESIS, April, 1994, pages 378-380 "Improved Synthesis of 1,4,5,8,9,12-HexaazatriphenylenehexacArboxylic Acid"

The present invention relates to an organic electroluminescent device and an organic electroluminescent display.

Organic electroluminescent devices (organic EL devices) have been actively developed in terms of their application to displays and lighting. The driving principle of an organic EL element is as follows. That is, holes and electrons are injected from the anode and the cathode, respectively, and they are transported in the organic thin film, and recombined in the light emitting layer to generate an excited state, and light emission is obtained from this excited state. In order to increase the luminous efficiency, it is necessary to efficiently inject holes and electrons and transport them into the organic thin film. However, the carrier movement in the organic EL element is limited by the energy barrier between the electrode and the organic thin film or by the low carrier mobility in the organic thin film, so that there is a limit in improving the luminous efficiency.

On the other hand, as another method of improving luminous efficiency, the method of laminating | stacking several light emitting layers is mentioned. For example, in some cases, higher luminous efficiency may be obtained than in the case of one layer by laminating the orange light emitting layer and the blue light emitting layer in a complementary color to be in direct contact with each other. For example, in the case where the luminous efficiency of the blue light emitting layer is 10 cd / A and the luminous efficiency of the orange light emitting layer is 8 cd / A, the luminous efficiency of 15 cd / A can be obtained when the light emitting efficiency of the blue light emitting layer is laminated. there was.

However, when a plurality of light emitting layers are stacked, there is a problem that cavity adjustment becomes difficult because there are a plurality of light emitting regions. That is, the light emitted from the light emitting layer includes light emitted to the anode side and light emitted to the cathode side, and since the cathode is generally formed as a reflective electrode, light emitted to the cathode side is reflected from the cathode and emitted to the anode side. do. As described above, in the organic EL device, since optical interference due to the dual path exists, it is important to design to increase the amount of light emitted from the device by adjusting the optical distance in the device.

In Japanese Patent Application Laid-Open No. 2003-272860 and Japanese Patent Laid-Open No. 2004-342614, in the organic EL device in which a plurality of light emitting units are stacked, the above-described cavity adjustment is performed by adjusting the respective optical film thicknesses for each light emitting unit. have. However, if the thickness of the layer constituting the light emitting unit is adjusted for each light emitting unit, the carrier balance in each light emitting unit is changed, and the device characteristics themselves are greatly changed so that a desired characteristic cannot be obtained.

In the organic EL device, a charge transport layer, a charge injection layer or the like for transferring holes or electrons is generally provided between the electrode and the light emitting layer.

Japanese Laid-Open Patent Publication No. 2003-151776 discloses the lowest conduction band of an electron trap layer base material in a structure in which a hole injection layer, a hole transport layer, an electron trap layer, a light emitting layer, and an electron transport layer are stacked from an anode side to a cathode side. It is proposed to make it lower than the conduction band lowest level of a transport layer base material, and the conduction band minimum level of a light emitting layer base material. This prevents deterioration of the hole transport layer base material on the anode side.

In Japanese Unexamined Patent Application Publication No. 2004-207000, it is proposed to interpose a mixed layer in which constituent materials of adjacent hole transport layers are mixed at an interface between two adjacent hole transport layers, whereby two adjacent charge transport layers are provided. It is described that the adhesion between the liver can be improved, and the luminous efficiency and luminance life can be improved.

In Japanese Unexamined Patent Publication No. 2003-229269, it is proposed to control electron transport efficiency by alternately stacking a cathode buffer layer and an electron transport layer between the cathode and the light emitting layer alternately.

Conventionally, tertiary arylamine-based materials such as NPB (N, N'-di (naphthace-1-yl) -N, N'-diphenylbenzidine) are used as the hole transporting layer. When the thickness of the hole transport layer made of NPB or the like is increased, there is a problem that the drive voltage is increased because the carrier mobility of the hole transport material such as NPB is low. Therefore, conventionally, there has been a demand for an element structure of an organic EL element capable of reducing a driving voltage even when the thickness of an NPB or the like is increased.

In addition, in the organic EL display, there is a problem that a viewing angle dependency exists and that the color tone of the image is slightly changed when it is oblique to the front face. The viewing angle dependence in the organic EL display is not so large that the image is inverted when viewed obliquely like the liquid crystal display. The reason for this is that the difference in refractive index between the organic layer and the inorganic layer (ITO film) and the like constituting the organic EL element is large, and the cathode in the organic EL element acts as a mirror, causing optical interference in the element. It is preferable to reduce this minute viewing angle dependency because it impairs the display quality of the organic EL display. However, no proposal has yet been made to sufficiently reduce the viewing angle dependence.

On the other hand, an organic EL display is expected as a display for portable devices, and low power consumption and long lifetime are demanded. The present applicant has found that by stacking a plurality of light emitting layers through an intermediate unit, the power consumption can be reduced and the life can be improved (Japanese Patent Laid-Open No. 2006-49396). However, this patent document does not disclose anything about the viewing angle dependency.

Japanese Laid-Open Patent Publication No. 2003-272860 discloses stacking a plurality of light emitting layers. In two light sources, the distance between the light source closer to the reflective electrode and the reflective electrode is 1/4 lambda and is far from the reflective electrode. It is described that the luminance and the luminous efficiency are improved by setting the distance between the light source and the reflective electrode to 3 / 4λ. In this way, the intensity of the light in the front direction is surely maximized. However, in the inclination direction (for example, 60 °), the intensity decreases conversely, and the viewing angle dependence is increased, and the display quality is significantly reduced.

SYNTHESIS, April, 1994, pages 378-380 “Improved Synthesis of 1,4,5,8,9,12-HexaazatriphenylenehexacArboxylic Acid” discloses the synthesis of hexaazatriphenylene derivatives used in the present invention.

A first object of the present invention is to provide an organic EL element in which a plurality of light emitting units are stacked, which can easily adjust a cavity without changing the film thickness in each light emitting unit, and an organic EL display device using the same. It's there.

A second object of the present invention is to provide an organic EL element and an organic EL display device which can adjust a cavity, have high luminous efficiency, reduce driving voltage, and increase reliability.

A third object of the present invention is to provide an organic EL device capable of reducing the viewing angle dependency.

<1st aspect of this invention>

The organic EL device of the present invention comprises a cathode; anode; And a cavity adjusting layer having a plurality of light emitting units disposed between the cathode and the anode via an intermediate unit, and adjusting an optical distance from the light emitting position of each light emitting unit to the anode between the light emitting unit closest to the anode and the anode; It is characterized by further including an electron extraction layer provided adjacent to the cavity adjustment layer on the light emitting unit side.

In the present invention, the cavity adjusting layer is provided between the light emitting unit closest to the anode and the cathode, so that the optical distance from the light emitting position of each light emitting unit to the anode can be adjusted by adjusting the film thickness of the cavity adjusting layer. For this reason, the cavity can be adjusted without changing the film thickness in each light emitting unit. For this reason, a cavity can be adjusted without providing a big change in element characteristic. Therefore, according to the present invention, optical interference by the optical path when it is emitted from the light emitting position of each light emitting unit to the anode side, which is a transparent electrode, and the optical path emitted to the cathode side and reflected by the cathode, which is a reflective electrode, is directed toward the anode side. This can increase the amount of light extracted from the device.

In the present invention, the electron extraction layer is provided adjacent to the cavity adjustment layer on the light emitting unit side of the cavity adjustment layer. The electron withdrawing layer extracts electrons from the layer adjacent to the light emitting unit side, and supplies the generated holes to the light emitting unit side and supplies the extracted electrons to the anode side. The layer adjacent to the electron extraction layer may be a layer in the light emitting unit, or may be a layer not included in the light emitting unit. That is, the electron extraction layer may be adjacent to the light emitting unit, or may be adjacent to layers other than the light emitting unit.

By providing an electron extraction layer on the light emitting unit side of the cavity adjustment layer, the life characteristics of the organic EL element can be extended.

In this invention, the optical distance from the light emission position of each light emitting unit to an anode is adjusted by adjusting the film thickness of a cavity adjustment layer. For this reason, it is preferable that the material which comprises a cavity adjustment layer is a material with little influence on the light emission characteristic by a change of film thickness. In general, when the thickness of the organic layer constituting the organic EL element becomes thick, the driving voltage is increased or the luminous efficiency is lowered. In terms of reducing this effect, the material constituting the cavity adjusting layer in the present invention is preferably a material having a carrier mobility of 1 × 10 ⁻⁶ cm 2 / Vs or more, more preferably 1 × 10 ⁻⁴ cm 2 / Vs A material having the above carrier mobility is used. It is preferable that the cavity adjustment layer in this invention is formed from a hole-transport material, Therefore, it is preferable that the hole mobility is 1x10 <^-6> cm <2> / Vs or more, More preferably, it is 1x10 <^-4> cm <2> / Vs. That's it. Carrier mobility can be measured by the Time of Flight method.

In addition, in order that the cavity adjustment layer in the present invention can take out the light from the light emitting unit to the outside without loss, the refractive index is preferably within the range of 1.6 to 1.8 in consideration of matching with other organic layers. Do. The refractive index can be measured with an ellipsometer, for example, by forming a thin film of a measurement object having a thickness of 100 nm on a silicon substrate. As a light source of an ellipsometer, the He-Ne laser (wavelength 632.8 nm) of 1 mW of output can be used, for example.

Moreover, it is preferable that the material which comprises the cavity adjustment layer in this invention is a film thickness of 1 micrometer, and is a material which transmits 50% or more of visible light in the wavelength range of 400 nm-700 nm. As a result, the light from each light emitting unit can be prevented from being absorbed by the cavity adjusting layer and greatly attenuated.

As described above, the cavity layer in the present invention can be formed of a hole transporting material. An arylamine type hole transport material is mentioned as such a hole transport material.

Further, in the present invention, a second electron withdrawing layer may be provided on the anode side adjacent to the cavity adjusting layer. By providing the second electron withdrawing layer on the anode side, the heat resistance and light resistance of the organic EL element can be improved.

The electron extraction layer in the present invention can be formed of, for example, a pyrazine derivative represented by the structural formula shown below.

(Wherein Ar represents an aryl group, R represents hydrogen, an alkyl group having 1 to 10 carbon atoms, an alkyloxy group, a dialkylamine group, or F, Cl, Br, I or CN)

In the present invention, the electron withdrawing layer can be formed more preferably with a hexaazatriphenylene derivative represented by the structural formula shown below.

(Wherein R represents hydrogen, an alkyl group having 1 to 10 carbon atoms, an alkyloxy group, a dialkylamine group, or F, Cl, Br, I or CN)

In the organic EL device of the present invention, a plurality of light emitting units are provided between the cathode and the anode. These light emitting units are stacked via an intermediate unit. As an intermediate unit, it is preferable to have an electron extraction layer for drawing an electron from the adjacent layer adjacent to a cathode side, and the electron injection layer adjacent to the anode side of an electron extraction layer. In addition, the absolute value of the energy level of the lowest comolecule orbital (LUMO) of the electron-extracting layer | LUMO (A) | and the absolute value of the energy level of the highest point molecular orbital (HOMO) of the adjacent layer | HOMO (B) | B) |-| LUMO (A) | The absolute value of the energy level of the lowest co-molecular orbital (LUMO) of the electron injection layer in relation of ≤ 1.5 eV | LUMO (C) | or the absolute value of the work function | WF (C) It is preferable that || is smaller than | LUMO (A) |.

The intermediate unit supplies holes generated by the withdrawal of electrons from the adjacent layer by the electron withdrawing layer provided in the intermediate unit to the light emitting unit located on the cathode side, and at the same time the withdrawn electrons are located on the anode side through the electron injection layer. Supply to the light emitting unit.

Hereinafter, in the description of the intermediate unit, the light emitting unit positioned on the cathode side will be described as the first light emitting unit and the light emitting unit positioned on the anode side as the second light emitting unit.

As described above, in the intermediate unit, the absolute value of the energy level of HOMO of the adjacent layer | HOMO (B) | and the absolute value of the energy level of LUMO of the electron withdrawing layer | LUMO (A) | | LUMO (A) | ≤ 1.5 eV, and it is preferable that the energy level of LUMO of an electron extraction layer is set to the value close to the energy level of HOMO of an adjacent layer. As a result, the electron withdrawing layer can withdraw electrons from the adjacent layer. Holes are generated in the adjacent layer by drawing out electrons from the adjacent layer. When the adjacent layer is provided in the first light emitting unit, holes are generated in the first light emitting unit. In addition, when the adjacent layer is provided between the electron withdrawing layer and the first light emitting unit, that is, when provided in the intermediate unit, holes generated in the adjacent layer are supplied to the first light emitting unit. The holes supplied to the first light emitting unit recombine with electrons from the cathode, and the first light emitting unit emits light.

On the other hand, the electrons drawn to the electron extraction layer move to the electron injection layer, are supplied to the second light emitting unit from the electron injection layer, recombine with holes supplied from the anode, and the second light emitting unit emits light accordingly.

In the intermediate unit, in order for the electron withdrawing layer to withdraw electrons from the adjacent layer, it is preferable that the energy level of the LUMO of the electron withdrawing layer is closer to the energy level of the HOMO of the adjacent layer than the energy level of the LUMO of the adjacent layer. That is, it is preferable that the absolute value | LUMO (B) | of the energy level of LUMO of the adjacent layer satisfies the following relationship.

| HOMO (B) |-| LUMO (A) ｜ <| LUMO (A) |-| LUMO (B) |

In addition, since the absolute value of the energy level of LUM0 of the material used as an electron extraction layer is generally smaller than the absolute value of the energy level of HOMO of an adjacent layer, in this case, the absolute value of each energy level is represented by the following relationship.

0eV <| HOMO (B) |-| LUMO (A) | ≤1.5eV

The absolute value of LUMO energy level | LUMO (C) | or the work function absolute value | WF (C) | of the electron injection layer is preferably smaller than the absolute value | LUMO (A) | of energy level of LUMO of the electron withdrawing layer. Accordingly, the electrons extracted from the electron extraction layer move to the electron injection layer and are supplied to the second light emitting unit from the electron injection layer.

It is preferable that an electron transport layer is provided between the electron injection layer and the second light emitting unit in the intermediate unit. It is preferable that the absolute value | LUMO (D) | of the energy level of LUMO of an electron carrying layer is smaller than the absolute value | LUMO (C) | of the energy level of LUMO of an electron injection layer, or the absolute value | WF (C) | of work function. When the electron transport layer is provided, electrons moved to the electron injection layer are supplied to the second light emitting unit through the electron transport layer. Therefore, the intermediate unit supplies the electrons extracted by the electron extraction layer to the second light emitting unit through the electron injection layer and the electron transport layer.

The electron extracting layer in the intermediate unit can be formed of the same material as the electron extracting layer provided adjacent to the cavity adjusting layer of the present invention. That is, it may be formed of a pyrazine derivative represented by the above structural formula, and more preferably may be formed of a hexaazatriphenylene derivative represented by the above structural formula.

The electron injection layer in the intermediate unit is preferably formed of, for example, alkali metals such as Li and Cs, alkali metal oxides such as Li ₂ O, alkaline earth metals, alkaline earth metal oxides and the like.

Further, the electron transporting layer in the intermediate unit can be formed of a material that is generally used as an electron transporting material in organic EL elements. For example, chelate metal complexes such as tris (8-quinolinate) aluminum derivatives, or o- or m- or p-phenanthroline derivatives, or sirol derivatives, oxadiazole derivatives, or triazole derivatives, etc. Can be mentioned.

Each of the light emitting units in the present invention may be formed of a single light emitting layer, or may be configured by stacking a plurality of light emitting layers in direct contact with each other. For example, it may be a white light emitting unit in which a blue light emitting layer and an orange light emitting layer are stacked.

In addition, it is preferable that the light emitting layer which comprises the light emitting unit in this invention is formed from a host material and a dopant material. If necessary, a carrier transportable second dopant material may be contained. The dopant material may be a singlet light emitting material or a triplet light emitting material (phosphorescent light emitting material).

An organic light emitting display according to the present invention is an organic electroluminescent element having an element structure sandwiched between an anode and a cathode, and an active element having an active element for supplying a display signal corresponding to each display pixel to the organic electroluminescent element. An organic electroluminescence display of a bottom emission type comprising a matrix driving substrate, an organic electroluminescent element disposed on an active matrix driving substrate, and an electrode provided on a substrate side of a cathode and an anode as a transparent electrode. The device is a cathode; anode; A plurality of light emitting units disposed through an intermediate unit between the cathode and the anode; A cavity adjusting layer provided between the light emitting unit closest to the anode and the anode; And an electron extraction layer provided adjacent to the cavity adjusting layer on the light emitting unit side, and the optical distance from the light emitting position of each light emitting unit to the anode is adjusted by adjusting the film thickness of the cavity adjusting layer. It is a light emitting display device.

An organic light emitting display device of a top emission type according to the present invention comprises: an organic electroluminescent device having a device structure sandwiched between an anode and a cathode; An active matrix driving substrate provided with an active element for supplying a display signal corresponding to each display pixel to the organic electroluminescent element; And a transparent sealing substrate provided opposite to the active matrix driving substrate, and an organic electroluminescent element is disposed between the active matrix driving substrate and the sealing substrate, and an electrode provided on the sealing substrate side of the cathode and the anode as a transparent electrode. An organic light emitting display device of one top emission type, the organic light emitting device comprising: a cathode; anode; A plurality of light emitting units disposed through an intermediate unit between the cathode and the anode; A cavity adjusting layer provided between the light emitting unit closest to the anode and the anode; And an electron extracting layer provided on the light emitting unit side adjacent to the cavity adjusting layer, and the optical distance from the light emitting position of each light emitting unit to the anode is adjusted by adjusting the film thickness of the cavity adjusting layer. It is a light emitting display device.

When the organic electroluminescent element is a white light emitting element, it is preferable that a color filter is arranged. In the case of the bottom emission type organic EL display device, it is preferable that a color filter is disposed between the active matrix driving substrate and the organic EL element. In the case of the top emission type organic EL display device, it is preferable that a color filter is disposed between the sealing substrate and the organic EL element.

In the case of the top emission type display device, the light emitted from the organic EL element is emitted from the sealing substrate on the side opposite to the side where the active matrix is provided. In general, an active matrix circuit is formed by stacking a plurality of layers. In the case of a bottom emission type, outgoing light is attenuated by the presence of such an active matrix driving substrate. Can emit light without receiving.

The light emitting device of the present invention is characterized by using the organic electroluminescent element of the present invention.

Second Aspect of the Invention

The organic EL device of the present invention comprises a cathode; anode; An intermediate unit disposed between the cathode and the anode; A first light emitting unit disposed between the cathode and the intermediate unit; A second light emitting unit disposed between the anode and the intermediate unit; And a cavity adjusting unit disposed between the intermediate unit and the second light emitting unit and installed adjacent to the intermediate unit,

The intermediate unit has a first electron withdrawing layer for withdrawing electrons from the cavity adjusting unit, and an electron injection layer adjacent to the anode side of the first electron withdrawing layer,

The cavity adjusting unit is provided adjacent to the cathode side of the first electron extracting layer, and is configured to extract electrons from the first cavity adjustment layer through which electrons are drawn out to the first electron extracting layer, and the electron supply layer adjacent to the cathode side. 2 electron-withdrawing layer,

The absolute value of the energy level of the lowest co-molecular orbital (LUMO) of the first electron withdrawing layer | LUMO (B) | and the absolute value of the energy level of the highest point molecular orbital (HOMO) of the first cavity adjusting layer | | HOMO (A) |-| LUMO (B) | The absolute value of the energy level of the lowest co-molecular orbital (LUMO) of the electron injection layer in relation of ≤1.5eV | LUMO (C) | or the absolute value of the work function | WF (C) | is smaller than | LUMO (B) |

Absolute value | LUMO (D) | of energy level of lowest comolecule orbital (LUMO) of 2nd electron withdrawing layer | absolute value | HOMO (E) | (E) |-| LUMO (D) | <1.5eV, and absolute value | LUMO (A) | and | LUMO (D) | of LUMO (D) | (A) | <| LUMO (D) |

In the present invention, an intermediate unit is provided between the first light emitting unit and the second light emitting unit, and a cavity adjusting unit is provided between the intermediate unit and the first light emitting unit so as to be adjacent to the intermediate unit. Therefore, the cavity can be adjusted by adjusting the film thickness of this cavity adjusting unit. The light emitted from the second light emitting unit is reflected by the intermediate unit, the cavity adjusting unit, and the cathode passing through the first light emitting unit, which is generally formed of a metal thin film, and then the first light emitting unit, the cavity adjusting unit, the intermediate unit, and the first light emitting unit. 1 is emitted to the outside through the light emitting unit and the anode. Therefore, by adjusting the film thickness of the cavity adjusting unit, the cavity of the light emitted from the second light emitting unit can be effectively adjusted.

The intermediate unit is provided with a first electron extracting layer for drawing electrons from the cavity adjusting unit, and an electron injection layer adjacent to the anode side of the first electron extracting layer.

The cavity adjusting unit is provided adjacent to the cathode side of the first electron extraction layer, and is configured to extract electrons from the first cavity adjustment layer through which electrons are drawn out to the first electron extraction layer, and the electron supply layer located on the cathode side. 2 electron withdrawing layers are provided.

In the intermediate unit, | LUM0 (B) | of the first electron extraction layer and | HOMO (A) | of the first cavity adjustment layer have a relationship of the following equation.

| HOMO (A) ｜-｜ LUMO (B) ｜ ≤1.5eV

Therefore, a 1st electron extraction layer can easily take out an electron from the adjoining 1st cavity adjustment layer.

Further, | LUMO (C) | or | WF (C) | of the electron injection layer adjacent to the anode side of the first electron extraction layer and | LUMO (B) | of the first electron extraction layer are related to the following equation. have.

| LUMO (C) | or | WF (C) | <| LUMO (B) |

Therefore, the electrons extracted by the first electron extraction layer are supplied to the electron injection layer, and are supplied to the second light emitting unit from the electron injection layer.

| LUMO (D) | of the 2nd electron extraction layer in a cavity adjustment unit, and the electron supply layer | HOMO (E) | adjacent to the cathode side of this 2nd electron extraction layer have a relationship of the following formula.

| HOMO (E) |-| LUMO (D) ｜ ≤1.5eV

  Therefore, a 2nd electron extraction layer can easily take out an electron from an electron supply layer.

In addition, | LUMO (A) | of the 1st cavity adjustment layer and | LUMO (D) | of the 2nd electron extraction layer have a relationship of the following formula.

｜ LUMO (A) ｜ <｜ LUMO (D) ｜

Therefore, the electrons extracted by the second electron extraction layer are blocked by the first cavity adjustment layer, and electrons are accumulated in the second electron extraction layer. For this reason, it is considered that a locally high electric field is applied, and even if the energy band is changed by this high electric field to increase the film thickness of the first cavity adjustment layer, it is possible to suppress the increase in the driving voltage.

In the intermediate unit of the present invention, the first electron extracting layer extracts electrons from the first cavity adjusting layer of the cavity adjusting unit, and supplies the extracted electrons to the second light emitting unit on the anode side through the electron injection layer. In the second light emitting unit, the holes supplied from the anode and the electrons combine to emit light. On the other hand, holes are generated in the first cavity adjustment layer from which electrons are drawn.

In the cavity adjusting unit, the second electron extracting layer extracts electrons from the adjacent electron supply layer, and the extracted electrons accumulate in the second electron extracting layer as described above, thereby generating a locally high electric field. Electrons accumulated in the second electron extraction layer combine with holes generated in the first cavity adjustment layer. Holes are generated in the electron supply layer in which the electrons are extracted, and the holes are supplied to the first light emitting unit on the cathode side, and the first light emitting unit emits light in combination with the electrons supplied from the cathode.

As described above, in the present invention, electrons are supplied from the intermediate unit and the cavity adjusting unit to the second light emitting unit on the anode side, and holes are supplied to the first light emitting unit on the cathode side, so that each light emitting unit can efficiently emit light. Can be. In addition, as described above, electrons accumulate in the second electron extracting layer, thereby locally applying a high electric field. For this reason, even if the film thickness of the 1st cavity adjustment layer in a cavity adjustment unit is made thick, since a rise of a drive voltage can be suppressed, high luminous efficiency is obtained.

In the present invention, the electrons are blocked by the first cavity adjustment layer of the cavity adjustment unit as described above. Therefore, since excessive supply of electrons to the anode side can be prevented, the device life can be lengthened and the reliability of the device can be improved.

In the present invention, the electron supply layer is preferably formed of a hole transporting material. If the light emitting layer provided in the 1st light emitting unit uses a hole transport material as a host material, this light emitting layer can be used as an electron supply layer. Therefore, in the present invention, the electron supply layer may be provided in the first light emitting unit.

In addition, in this invention, an electron supply layer may be a 2nd cavity adjustment layer provided in a cavity adjustment unit. In this case, the film thickness of not only a 1st cavity adjustment layer but also a 2nd cavity adjustment layer can be thickened, and it can be used for cavity adjustment.

In the present invention, the first and second cavity adjustment layers are preferably formed of a hole transporting material. A tertiary arylamine type material is mentioned as such a hole-transport material.

In the present invention, the cavity adjusting unit may have these layers in a plurality of repeating units by combining the first cavity adjusting layer and the second electron withdrawing layer. That is, the laminated structure of a 1st cavity adjustment layer / 2nd electron extraction layer / 1st cavity adjustment layer / 2nd electron extraction layer in a cavity adjustment unit, or a 1st cavity adjustment layer / 2nd electron extraction layer / 1st cavity adjustment It may have a laminated structure of a layer / second electron extraction layer / first cavity adjustment layer / second electron extraction layer. The preferred film thickness of the cavity adjusting layer is generally in the range of 10 to 700 nm. If the film thickness of the cavity adjustment layer is too thick, there arises a problem that the driving voltage becomes too high and the luminous efficiency is lowered. For this reason, when it is going to make the film thickness of a cavity adjustment layer thicker than this range, it is preferable to insert a 2nd electron extraction layer suitably, and to provide two or more repeating units of a 1st cavity adjustment layer and a 2nd electron extraction layer.

Also, in the present invention, an electron transport layer may be provided between the electron injection layer and the second light emitting unit in the intermediate unit. The absolute value | LUMO (F) | of the energy level of the lowest covalent orbital LUMO of this electron transport layer is set to be smaller than | LUMO (C) | or | WF (C) |.

Moreover, in this invention, it is preferable that | HOMO (A) | of a 1st cavity adjustment layer and | HOMO (D) | of a 2nd electron extraction layer have a relationship of a following formula.

| HOMO (A) ｜ <｜ HOMO (D) ｜

By discovering Equation (5), holes are accumulated at the interface between the first cavity adjusting layer and the second electron withdrawing layer, and it is thought that a higher electric field can be applied more locally, thereby lowering the driving voltage. .

In this invention, the pyrazine derivative represented by the structural formula shown below is mentioned as a material which forms a 1st and / or 2nd electron extraction layer.

&Lt; Formula 1 >

(Wherein Ar represents an aryl group, R represents hydrogen, an alkyl group having 1 to 10 carbon atoms, an alkyloxy group, a dialkylamine group, or F, Cl, Br, I or CN)

Moreover, it is more preferable that the material which forms the 1st and / or 2nd electron extraction layer of this invention is a hexaaza triphenylene derivative represented by the structural formula shown below.

<Formula 2>

(Wherein R represents hydrogen, an alkyl group having 1 to 10 carbon atoms, an alkyloxy group, a dialkylamine group, or F, Cl, Br, I or CN)

Further, in the present invention, an electron withdrawing promoting material for promoting electron withdrawal may be doped into the first and / or second electron withdrawing layer. It is preferable that the absolute value | LUMO (G) | of the energy level of the lowest co-molecular orbital (LUMO) of such electron withdrawal promoting material is in the relation of the following equation.

| HOMO (A) | or | HOMO (E) |> | LUMO (G) | ＞ | LUMO (B) | or | LUMO (D) |

It is preferable that the difference between | HOMO (A) | and | LUMO (G) | and the difference between | HOMO (E) | and | LUMO (G) | are preferably 1.5 eV or less. Due to such a difference, even if the difference between | HOMO (A) and | LUMO (B) | and the difference between | HOMO (E) and | LUMO (D) | are greater than 1.5 eV, for example 2.0 eV, electron withdrawal It becomes possible to easily carry out the extraction of electrons by the layer.

Each of the first light emitting unit and the second light emitting unit in the present invention may be a single light emitting layer, or may be a layer having a laminated structure in which a plurality of light emitting layers are stacked. For example, it may be a white light emitting unit in which an orange light emitting layer and a blue light emitting layer are stacked.

The organic electroluminescent display device of the present invention comprises an active matrix drive substrate provided with an organic electroluminescent element having an element structure sandwiched between an anode and a cathode, and an active element for supplying a display signal corresponding to each display pixel to the organic electroluminescent element. And an organic electroluminescent element disposed on an active matrix driving substrate, wherein the electrode disposed on the substrate side of the cathode and the anode is a transparent electrode, wherein the organic electroluminescent element is a cathode; anode; An intermediate unit disposed between the cathode and the anode; A first light emitting unit disposed between the cathode and the intermediate unit; A second light emitting unit disposed between the anode and the intermediate unit; And a cavity adjusting unit disposed between the intermediate unit and the second light emitting unit and installed adjacent to the intermediate unit, wherein the intermediate unit includes a first electron extracting layer for drawing electrons from the cavity adjusting unit, and a first electron extracting unit; The first cavity adjustment layer which has an electron injection layer adjacent to the anode side of a layer, and a cavity adjustment unit is provided adjacent to the cathode side of a 1st electron extraction layer, and an electron is drawn out to a 1st electron extraction layer, and a cathode side The absolute value | LUMO (B) | of 1st cavity adjustment layer which has a 2nd electron extraction layer for extracting an electron from the electron supply layer adjacent to the energy supply layer, and the lowest co-molecular orbital LUM0 of a 1st electron extraction layer. The absolute value of the energy level of the highest point molecular orbital (HOMO) of HOHO (A) | is in the relation of | HOMO (A) |-| LUMO (B) | ≤ 1.5 eV, and the lowest molecular orbital of the electron injection layer ( LUM0) absolute value of energy level | LUMO (C) | or The absolute value of the work function | WF (C) | is smaller than | LUMO (B) | and the absolute value of the lowest level molecular energy (LUMO) of the second electron withdrawing layer | LUMO (D) | The absolute value of the energy level of the highest point molecular orbital (HOMO) HOHO (E) is in the relationship of HOMO (E) -LUMO (D) 1.5 eV, and the lowest covalent orbital of the first cavity adjustment layer. The absolute value | LUMO (A) | and | LUMO (D) | of the energy level of (LUMO) are characterized by having a relationship of | LUMO (A) | <| LUMO (D) |.

In the organic electroluminescent display of the present invention, when the organic EL element is a white light emitting element, a color filter can be arranged between the organic EL element and the substrate to form a color display device.

According to another aspect of the present invention, an organic light emitting display device includes: an organic light emitting display device having an element structure sandwiched between an anode and a cathode; An active matrix driving substrate provided with an active element for supplying a display signal corresponding to each display pixel to the organic electroluminescent element; And a transparent sealing substrate provided opposite to the active matrix driving substrate, and an organic electroluminescent element is disposed between the active matrix driving substrate and the sealing substrate, and an electrode provided on the sealing substrate side of the cathode and the anode as a transparent electrode. An organic light emitting display device of one top emission type, the organic light emitting device comprising: a cathode; anode; An intermediate unit disposed between the cathode and the anode; A first light emitting unit disposed between the cathode and the intermediate unit; A second light emitting unit disposed between the anode and the intermediate unit; And a cavity adjusting unit disposed between the intermediate unit and the second light emitting unit and installed adjacent to the intermediate unit, wherein the intermediate unit includes a first electron extracting layer for drawing electrons from the cavity adjusting unit, and a first electron extracting unit; The first cavity adjustment layer which has an electron injection layer adjacent to the anode side of a layer, and a cavity adjustment unit is provided adjacent to the cathode side of a 1st electron extraction layer, and an electron is drawn out to a 1st electron extraction layer, and a cathode side An absolute value | LUMO (B) | and the first cavity adjustment layer of the energy level of the lowest covalent orbital (LUMO) of the first electron withdrawing layer, having a second electron withdrawing layer for withdrawing electrons from an electron supply layer adjacent to the second electron withdrawing layer; The absolute value of the energy level of the highest point molecular orbital (HOMO) of HOHO (A) | is in the relation of | HOMO (A) |-| LUMO (B) | ≤ 1.5 eV, and the lowest molecular orbital of the electron injection layer ( Absolute value of energy level of LUMO) LUMO (C) Absolute value | WF (C) | of work function is smaller than | LUMO (B) |, and absolute value | LUMO (D) | of energy level of lowest covalent orbital (LUMO) of second electron withdrawing layer and highest of electron supply layer The absolute value of the energy level | of the molecular molecular orbital (HOMO) | HOMO (E) | is in relation to | HOMO (E) |-| LUMO (D) | ≤1.5eV, and the lowest covalent orbital of the first cavity adjusting layer ( It is characterized in that the absolute value | LUMO (A) | and | LUMO (D) | of the energy level of LUMO) are in a relationship of | LUMO (A) | <| LUMO (D) |.

In the above organic electroluminescent display, when the organic EL element is a white light emitting element, a color filter can be arranged between the organic EL element and the sealing substrate to form a color display device.

Since the organic EL display device of the present invention includes the organic EL element of the present invention, the cavity can be adjusted for each emission color, and the driving voltage can be reduced to reduce the power consumption. Moreover, it can be set as the organic electroluminescence display which has high reliability.

<3rd aspect of this invention>

The present invention is a reflective electrode; A light extraction side electrode; And a first light emitting layer and a second light emitting layer disposed between the reflective electrode and the light extraction side electrode, wherein an optical distance between the light emitting position of the first light emitting layer and the reflective surface of the reflective electrode is (n / x). λ, and the optical distance between the light emitting position of the second light emitting layer and the reflecting surface of the reflective electrode is [(n + m) / 2 x] λ (λ is the center wavelength of the light to be extracted, n is odd, m is even, x is natural Commission).

According to the present invention, the optical distance between the light emitting position of the first light emitting layer and the reflecting surface of the reflecting electrode is (n / x) λ, and the optical distance between the position of the second light emitting layer and the reflecting surface of the reflecting electrode is [(n + m) / 2x] λ, the light emission intensity from the first light emitting layer in the front direction of the organic EL element can be maximized, and the light emission intensity from the second light emitting layer in the viewing angle 60 ° direction of the organic EL element can be maximized. have. That is, since the light emission intensity in the front direction from the first light emitting layer is maximized and the light emission intensity in the viewing angle 60 ° direction from the second light emitting layer is maximized, the viewing angle dependency can be reduced.

8 is a schematic view for explaining the above-described effects. In FIG. 8, the light emission position of a 1st light emitting layer is used as the light source 101, and the light emission position of a 2nd light emitting layer is used as the light source 102. In FIG. The optical distance between the light source 101 and the reflective surface 103 of the reflective electrode is set to (n / x) λ, and the optical distance between the light source 102 and the reflective surface 103 of the reflective electrode is [(n + m) / 2x]. λ.

As shown in FIG. 8, the optical distance between the light source 101 and the reflecting surface 103 of the reflecting electrode in the viewing angle 60 ° direction is (2n / x) λ, and the reflecting surface of the light source 102 and the reflecting electrode ( The optical distance between 103 is [(n + m) / x] λ. Therefore, in the frontal direction, the maximum light emission intensity is obtained because the optical distance between the light source 101 and the reflective surface 103 of the reflective electrode becomes an odd multiple of the center wavelength? Of the light emission to be taken out and the optical distance satisfies the resonance condition.

On the other hand, since the optical distance between the light source 102 and the reflecting surface of the reflective electrode becomes an odd multiple of lambda in the viewing angle of 60 °, the light emission intensity from the light source 102 is maximized.

Therefore, since the light emission intensity from the first light emitting layer to the front direction is maximized and the light emission intensity from the second light emitting layer to the viewing angle of 60 ° is maximized, the viewing angle dependency can be reduced.

In FIG. 8, the light source 101 is set at a position closer to the reflecting surface 103 of the reflective electrode than the light source 102, but the present invention is not limited thereto, and the light source 102, that is, the second light emitting layer is provided. May be disposed at a position closer to the reflecting surface 103 of the reflective electrode than the light emitting position of the light source 101, that is, the first light emitting layer.

In this invention, it is preferable that the 1st light emitting layer and the 2nd light emitting layer are laminated | stacked through the intermediate unit.

In addition, when the first light emitting layer is disposed between the reflective electrode and the intermediate unit, and the second light emitting layer is disposed between the light extraction side electrode and the intermediate unit, a first cavity adjustment layer is provided between the reflective electrode and the first light emitting layer. It is preferable that a second cavity adjustment layer is provided between the intermediate unit and the second light emitting layer. By adjusting the film thickness of these first cavity adjusting layer and the second cavity adjusting layer, the optical distance between the light emitting position of the first light emitting layer and the reflecting surface of the reflecting electrode and the optical between the light emitting position of the second light emitting layer and the reflecting surface of the reflecting electrode The distance can be easily adjusted.

It is preferable that a 1st cavity adjustment layer and a 2nd cavity adjustment layer consist of a hole-transport material.

Moreover, in this invention, it is preferable that an intermediate unit consists of an electron extraction layer, an electron injection layer, and an electron carrying layer. In the present invention, one of the reflective electrode and the light extraction side electrode becomes the anode and the other becomes the cathode, but in the intermediate unit, the electron extraction layer is provided on the cathode side. The electron injection layer is provided adjacent to the anode side of the electron extraction layer. The electron transport layer is provided adjacent to the anode side of the electron injection layer.

In the intermediate unit configured as described above, the electron withdrawing layer withdraws electrons from the adjacent layer adjacent to the anode side, and supplies the withdrawn electrons to the anode side through the electron injection layer and the electron transporting layer, and is adjacent by the withdrawal of the electrons. Holes generated in the layer are supplied to the cathode side. For this reason, light emission is performed efficiently in the light emitting layers on both sides with the intermediate unit in between.

Absolute value | LUMO (A) | of energy level of lowest comolecule orbital (LUM0) of electron withdrawing layer | absolute value | HOMO (B) | |-| LUMO (A) | The absolute value | LUMO (C) | or the absolute value of work function | WF (C) | It is preferable that it is smaller than | LUMO (A) |.

The intermediate unit supplies holes generated by the withdrawal of electrons from the adjacent layer by the electron withdrawing layer provided in the intermediate unit to the light emitting unit located on the cathode side, and at the same time the withdrawn electrons are located on the anode side through the electron injection layer. Supply to the light emitting unit.

In the following description of the intermediate unit, the light emitting layer located on the cathode side will be described as the first light emitting layer and the light emitting layer located on the anode side as the second light emitting layer.

As described above, in the intermediate unit, the absolute value | HOMO (B) | of the energy level of the HOMO of the adjacent layer and the absolute value | LUMO (A) | of the LUMO of the electron extracting layer are | HOMO (B) |- | LUMO (A) | ≤ 1.5 eV, and it is preferable that the energy level of LUMO of an electron extraction layer is set to the value close to the energy level of HOMO of an adjacent layer. As a result, the electron withdrawing layer can withdraw electrons from the adjacent layer. Holes are generated in the adjacent layer by drawing out electrons from the adjacent layer. When the adjacent layer is provided in the first light emitting layer, holes are generated in the first light emitting layer. Further, when the adjacent layer is provided between the electron withdrawing layer and the first light emitting layer, that is, when provided in the intermediate unit, holes generated in the adjacent layer are supplied to the first light emitting layer. The holes supplied to the first light emitting layer recombine with electrons from the cathode, whereby the first light emitting layer emits light.

On the other hand, the electrons drawn to the electron extraction layer move to the electron injection layer, are supplied to the second emission layer from the electron injection layer and the electron transport layer, recombine with holes supplied from the anode, and the second emission layer emits light accordingly.

In the intermediate unit, in order for the electron withdrawing layer to withdraw electrons from the adjacent layer, it is preferable that the energy level of the LUMO of the electron withdrawing layer is closer to the energy level of the HOMO of the adjacent layer than the energy level of the LUMO of the adjacent layer. That is, it is preferable that the absolute value | LUMO (B) | of the energy level of LUMO of the adjacent layer satisfies the following relationship.

| HOMO (B) |-| LUMO (A) ｜ <| LUMO (A) |-| LUMO (B) |

In addition, since the absolute value of the energy level of LUMO of the material used as an electron extraction layer is generally smaller than the absolute value of the energy level of HOMO of an adjacent layer, in this case, the absolute value of each energy level is represented by the following relationship.

0eV <| HOMO (B) |-| LUMO (A) | ≤1.5eV

The absolute value of LUMO energy level | LUMO (C) | or the work function absolute value | WF (C) | of the electron injection layer is preferably smaller than the absolute value | LUMO (A) | of energy level of LUMO of the electron withdrawing layer. Accordingly, the electrons extracted from the electron extraction layer move to the electron injection layer and are supplied to the second light emitting layer from the electron injection layer and the electron transport layer.

An electron transport layer is provided between the electron injection layer and the second light emitting layer in the intermediate unit. It is preferable that the absolute value | LUMO (D) | of the energy level of LUM0 of an electron carrying layer is smaller than the absolute value | LUMO (C) | of the energy level of LUMO of an electron injection layer | or the absolute value | WF (C) | of work function. The electrons moved to the electron injection layer pass through the electron transport layer and are supplied to the second light emitting layer.

The electron extraction layer in the present invention can be formed of, for example, a pyrazine derivative represented by the structural formula shown below.

&Lt; Formula 1 >

(Wherein Ar represents an aryl group, R represents hydrogen, an alkyl group having 1 to 10 carbon atoms, an alkyloxy group, a dialkylamine group, or F, Cl, Br, I or CN)

In this invention, More preferably, an electron extraction layer can be formed from the hexaaza triphenylene derivative represented by the structural formula shown below.

<Formula 2>

(Wherein R represents hydrogen, an alkyl group having 1 to 10 carbon atoms, an alkyloxy group, a dialkylamine group, or F, Cl, Br, l or CN)

The electron injection layer in the intermediate unit is preferably formed of, for example, alkali metals such as Li and Cs, alkali metal oxides such as Li ₂ O, alkaline earth metals, alkaline earth metal oxides and the like.

In addition, the electron carrying layer in an intermediate unit can be formed from the material generally used as an electron carrying material in organic electroluminescent element. For example, chelate metal complexes such as tris (8-quinolinate) aluminum derivatives, or o- or m- or p-phenanthroline derivatives, or sirol derivatives, oxadiazole derivatives, or triazole derivatives, etc. Can be mentioned.

In this invention, the 1st light emitting layer and the 2nd light emitting layer are laminated | stacked in the thickness direction of an element, and are light emitting layers which respectively emit the same color. It may be a monochromatic light emitting layer such as red (R), green (G), or blue (B), or may be a white light emitting layer. The white light emitting layer may be a white light emitting layer having a structure in which an orange light emitting layer and a blue light emitting layer are stacked.

If the optical distance prescribed | regulated by this invention is a micro range each, even if it deviates from (n / x) (lambda) and [(n + m) / 2x] (lambda), the effect of this invention is acquired. Therefore, the optical distance prescribed | regulated by this invention can be in the range of +/- 10% of these values.

<Effects of the first to third aspects of the present invention>

The organic EL element of the first aspect of the present invention is an organic EL element in which a plurality of light emitting units are stacked, and the cavity can be easily adjusted without changing the film thickness in each light emitting unit. Therefore, it can be set as the organic electroluminescent element which has a desired emission color and is high in the amount of light extraction from organic electroluminescent.

According to the second aspect of the present invention, it is possible to provide an organic EL element and an organic EL display device using the same, which can adjust the cavity, have high luminous efficiency, reduce driving voltage, and increase reliability.

According to the third aspect of the present invention, at least a first light emitting layer and a second light emitting layer are provided as light emitting layers, and the optical distance between the light emitting position of the first light emitting layer and the reflecting surface of the reflecting electrode is (n / x) λ, By setting the optical distance between the light emitting position of the two light emitting layers and the reflective surface of the reflective electrode to be [(n + m) / 2x] λ, the viewing angle dependency of the organic EL element can be reduced.

<Description of the Preferred Embodiment>

<1st aspect of this invention>

BRIEF DESCRIPTION OF THE DRAWINGS It is typical sectional drawing which shows the organic electroluminescent element which concerns on this invention. An anode 1 made of an ITO (indium tin oxide) film is formed on a glass substrate, and a hole injection layer 2 made of a fluorocarbon (CFx) layer is formed on the anode 1.

On the hole injection layer 2, a cavity adjustment layer 3 made of a hole transporting material such as NPB is formed. The electron extraction layer 4 is formed on the cavity adjustment layer 3.

The first light emitting unit 5 and the second light emitting unit 7 are provided on the electron extracting layer 4, and an intermediate unit 6 is provided between the first light emitting unit 5 and the second light emitting unit 7. Is installed. The first light emitting unit 5 is constituted by stacking the blue light emitting layer 5a on the orange light emitting layer 5b, and the second light emitting unit 7 similarly stacks the blue light emitting layer 7a on the orange light emitting layer 7b. It is comprised by doing. Thus, the first light emitting unit 5 and the second light emitting unit 7 are white light emitting units.

The intermediate unit 6 includes an electron transport layer 6c provided on the blue light emitting layer 5a; An electron injection layer 6b provided on the electron transport layer 6c; And an electron extraction layer 6a provided on the electron injection layer 6b.

The electron transport layer 8 is provided on the second light emitting unit 7, and the electron injection layer 9 is provided on the electron transport layer 8. The cathode 10 is provided on the electron injection layer 9.

In the embodiment shown in FIG. 1, the light emission from the first light emitting unit 5 is emitted toward the anode 1 and also toward the cathode 10. The light emitted from the cathode 10 is reflected from the surface of the cathode 10 toward the anode 1 because the cathode 10 is formed of a reflective electrode. The light emitted from the second light emitting unit 7 is also emitted to the anode 1 side and is emitted to the cathode 10 side, and the light reflected from the surface of the cathode 10 is directed toward the anode 1 side.

Therefore, it is necessary to adjust the cavity to adjust the interference of these lights to increase the amount of light emitted from the organic EL element. In the present invention, since the cavity adjusting layer 3 is provided, the anode 1 is removed from each light emitting position of the first light emitting unit 5 and the second light emitting unit 7 by adjusting the film thickness of the cavity adjusting layer 3. The optical distance up to) can be adjusted and the cavity can be easily adjusted.

In this embodiment, an intermediate unit 6 is provided between the first light emitting unit 5 and the second light emitting unit 7. The electron extracting layer 6a of the intermediate unit 6 extracts electrons from the adjacent orange light emitting layer 7b, supplies holes generated accordingly to the second light emitting unit 7 side, and simultaneously injects the extracted electrons. It supplies to the 1st light emitting unit 5 via the layer 6b and the electron carrying layer 6c. The second light emitting unit 7 emits light by recombining the holes supplied to the second light emitting unit 7 with electrons supplied from the cathode 10. In addition, electrons supplied to the first light emitting unit 5 are recombined with holes supplied from the anode 1 so that the first light emitting unit 5 emits light. Therefore, by providing the intermediate unit 6, the first light emitting unit 5 and the second light emitting unit 7 can be efficiently emitted.

The electron extraction layer 4 is provided on the side of the first light emitting unit 5 adjacent to the cavity adjustment layer 3. By providing the electron withdrawing layer 4, the lifetime characteristic of an element can be improved as mentioned later.

Moreover, in this invention, a 2nd electron extraction layer can be provided in a cathode side. That is, a 2nd electron extraction layer can also be provided in the hole injection layer 2 side adjacent to the cavity adjustment layer 3. By providing a 2nd electron extraction layer, the heat resistance and light resistance of an element can be improved.

[Production of White Light-Emitting Element] (Examples 1 to 7 and Reference Examples 1 to 5)

The organic EL devices of Examples 1 to 7 and Reference Examples 1 to 5 having the structure described with reference to FIG. 1 were manufactured. The composition of each layer is as shown in Table 1.

The fluorocarbon layer, which is a hole injection layer, is formed by plasma polymerization of CHF ₃ gas. The thickness of the fluorocarbon layer was 1 nm.

The cavity adjustment layer was formed of NPB as shown in Table 2. NPB is N, N'-di (naphthasen-1-yl) -N, N'- diphenylbenzidine, and has the following structure.

The first electron withdrawing layer and the second electron withdrawing layer were formed of HAT-CN6. HAT-CN6 is hexaazatriphenylene hexacarbonitrile and has the following structure.

The cavity adjustment layer and the 1st and 2nd electron extraction layer were formed so that it might become the film thickness shown in Table 2. In addition, the unit is nm.

As shown in Table 1, the first light emitting unit and the second light emitting unit are constituted by laminating a blue light emitting layer on the orange light emitting layer.

The orange light emitting layer is formed by using 80% by weight of NPB as a hole transporting material as a host material, 20% by weight of TBADN, and 3% by weight of DBzR as an orange light emitting dopant based on 100% by weight of the total of NPB and TBADN. have. In this case, however, the TBADN functions as an energy transfer assist dopant for transferring excitation energy from the host material to DBzR, an orange light emitting dopant. Here, the energy transfer assisted dopant refers to a material whose LUM0 (lowest molecular orbital) level and energy gap have a value between the host and the light emitting dopant, and refers to a dopant having a role of efficiently transferring excitation energy from the host to the light emitting dopant. Indicates.

TBADN is 2-tert-butyl-9,10-di (2-naphthyl) anthracene and has the following structure.

DBzR is 5,12-bis {4- (6-methylbenzothiazol-2-yl) phenyl} -6,11- diphenylnaphthacene, and has the following structure.

The blue light emitting layer uses TBADN, which is an electron transporting material, as a host material, NPB is used as a carrier transport assist dopant, and TBP is used as a blue light emitting dopant. The content of TBADN is 80% by weight, the content of NPB is 20% by weight, and the content of TBP is 2.5% by weight relative to 100% by weight of the total of TBADN and NPB. Here, the carrier movement assist dopant is a material having a higher carrier mobility than the host material, and promotes injection of one carrier, balances both carrier densities in the light emitting layer, and increases the recombination probability, thereby improving luminous efficiency. The height represents the dopant that has a role. In this case, NPB, which has a higher hole transport mobility than TBADN, is contained in TBADN, which is an electron transporting material, to play a role in assisting the movement of holes in the blue light emitting layer to increase luminous efficiency.

TBP is 2,5,8,11-tetra- tertiary-butylperylene and has the following structure.

The electron transport layer is formed of BCP. BCP is 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline and has the following structure.

As shown in Table 1, the intermediate unit forms an electron transporting layer with BCP, an electron injection layer with Li ₂ O, and an electron extracting layer with HAT-CN 6.

The electron injection layer is formed of LiF, and the cathode is formed of Al.

The thickness of each layer is as Table 1 and Table 2 showing. Here, the unit is nm.

Table 2 shows driving voltages, chromaticities, and luminous efficiencies of the organic EL elements of Examples 1 to 7 and Reference Examples 1 to 6, respectively.

As shown in Table 2, when the film thickness of the cavity adjustment layer is increased, the driving voltage slightly increases, and the luminous efficiency tends to decrease slightly, but it is understood that the effect on chromaticity is small. Therefore, it can be seen that cavity adjustment is easier than in the case of changing the film thickness of each conventional light emitting unit.

2 is a diagram showing a relationship between driving time and emission intensity of Examples 1 to 2 and Reference Examples 1 to 4; As shown in FIG. 2, Examples 1 to 2 and Reference Example 4 provided with the first electron extraction layer had higher emission intensity at longer driving time than those of Reference Examples 1 to 3 without the first electron extraction layer. It can be seen that the life characteristics are improved. Therefore, it can be seen that the life characteristics are improved by providing the first electron withdrawing layer.

3 is a diagram showing the relationship between the film thickness of the cavity adjustment layer and the driving voltage. From the result shown in FIG. 3, it is thought that it is preferable to exist in the range of 10 nm-600 nm as a film thickness of a cavity adjustment layer.

4 is a cross-sectional view showing an organic EL display device of an embodiment according to the present invention. In this organic EL display layer, light emission in each pixel of R (red), G (green), and B (blue) is driven by using a TFT (thin film transistor) as an active element. Referring to Fig. 4, the channel region 11 made of a polysilicon layer is formed on a transparent substrate such as glass (not shown). A drain electrode 12d and a source electrode 12s are formed on the channel region 11, and a gate electrode 14 is provided between the drain electrode 12d and the source electrode 12s via a gate insulating film 13. do. The insulating layer 15 is provided on the gate electrode 14. Each insulating layer is made of SiN _x and / or SiO ₂ or the like.

The first planarization film 16 is formed on the drain electrode 12d and the source electrode 12s. A through hole is formed in the first planarization film 16 on the drain electrode 12d, and an anode 1 made of an ITO film formed on the first planarization film 16 is introduced into the through hole. . The hole injection layer 2 is formed on the anode 1 in the pixel region. In portions other than the pixel region, the second planarization film 17 is formed.

According to the present invention, the cavity adjustment layer 3 and the electron withdrawing layer 4 are formed on the hole injection layer 2. The cavity layer 3 and the electron withdrawing layer 4 are shown as one layer in FIG. 4. As shown in FIG. 4, the cavity adjustment layer 3 and the electron extraction layer 4 are formed independently for each pixel of RGB. This is because the optimum film thickness of the cavity adjusting layer is different in each pixel of RGB, and it is preferable to form each pixel individually for each RGB.

The first light emitting unit 5, the intermediate unit 6, and the second light emitting unit 7 are independently formed for each pixel on the cavity adjustment layer 3 and the electron extraction layer 4 of each pixel. The electron transport layer 8 is formed on the second light emitting unit 7. The electron transport layer 8 is interposed between the cavity adjustment layer 3, the electron extraction layer 4, the first light emitting unit 5, the intermediate unit 6, and the second light emitting unit 7 independently stacked for each pixel. It is formed to fill the groove.

The electron injection layer 9 and the cathode 10 are formed on the electron transport layer 8. In FIG. 4, the electron injection layer 9 and the cathode 10 are shown in one layer. The protective layer 18 is formed on the cathode 10.

As shown in FIG. 4, the cavity in each pixel can be adjusted by appropriately adjusting the film thickness of the cavity adjustment layer 3 formed for each pixel for each pixel.

Although the embodiment shown in FIG. 4 is a back emission type organic EL display device in which light is emitted toward the substrate side, electron injection is performed on the cathode 10 by reversing the vertical relationship between the positions of the anode 2 and the cathode 10. By laminating the layer 9, the electron transport layer 8, the second light emitting unit 7, the intermediate unit 6, the first light emitting unit 5, the electron extracting layer 4 and the cavity adjusting layer 3 in this order The organic EL display device can be a top emission type that emits light on the opposite side to the substrate.

In the organic EL display device shown in Fig. 4, a pixel region is provided to form a display device. However, the organic EL light emitting device such as a backlight light source can be formed by providing the light emitting layer as a whole.

Second Aspect of the Invention

5 is a diagram schematically showing energy levels of HOMO and LUM0 of each layer constituting the intermediate unit and the cavity adjusting unit in the organic EL device of the embodiment according to the present invention. In the present embodiment, the intermediate unit 21 is composed of the first electron extraction layer 23, the electron injection layer 24, and the electron transport layer 28. The cavity adjustment unit 22 is comprised from the 1st cavity adjustment layer 25 and the 2nd electron extraction layer 26. As shown in FIG. The electron supply layer 27 is provided on the cathode side of the second electron extraction layer 26.

In Fig. 5, it shows a first electron take-LUMO the L _B, HOMO of the layer 23 to H _B. In addition, there is shown the LUMO of the electron injection layer 24 represents the LUMO as L _C, represents the LUM0 of the electron transport layer 28 as L _F, the first cavity layer 25, the L _A, HOMO by H _A. Further, a represents 2, the HOMO of the electron take-off layer, represents the LUMO of the (26), L _D, the HOMO as H _D electron supply layer 27 as H _E.

Referring to Fig. 5, in the organic EL device according to the present invention, the difference between the absolute values of L _B of the first electron extraction layer and H _A of the first cavity adjustment layer 25 is 1.5 eV or less. Therefore, the first electron extraction layer 23 can easily withdraw electrons from the first cavity adjustment layer 25. The absolute value of L _C of the electron injection layer 24 was smaller than the absolute value of L _B of the first electron extraction layer 23, and the absolute value of L _F of the electron transport layer 28 became smaller than the absolute value of L _C. Therefore, the electrons drawn out by the first electron extraction layer 23 pass through the electron injection layer 24 and the electron transport layer 28 and are supplied to the anode side.

In the present invention, the difference between the absolute value of L _D of the second electron extracting layer 26 and the absolute value of H _E of the electron supply layer 27 is 1.5 eV or less. Therefore, the second electron extraction layer 26 can easily withdraw electrons from the electron supply layer 27. Since the absolute value of L _A of the first cavity adjustment layer is smaller than the absolute value of L _D of the second electron extraction layer 26, the electrons drawn out by the second electron extraction layer 26 are transferred to the first cavity adjustment layer ( It is blocked by 25 and accumulated in the second electron withdrawing layer 26. Accordingly, the driving current can be reduced because a locally high electric field is applied to deform the energy level.

Holes are generated in the electron supply layer 27 from which electrons are drawn, and the holes are supplied to the cathode side.

In the present invention, as described above, the electrons can be supplied from the intermediate unit 21 and the cavity adjusting unit 22 to the anode side, and the holes can be supplied to the cathode side. Therefore, the light emitting unit located on the anode side and the light emitting unit located on the cathode side can be efficiently emitted. In addition, as described above, since a locally high electric field is applied, the driving voltage can be reduced, and even if the film thickness of the first cavity adjustment layer 25 is increased, the rise of the driving voltage can be suppressed.

In addition, since excessive supply of electrons to the anode side can be suppressed by the first cavity adjustment layer 25, the lifetime characteristics of the device can be improved and reliability can be improved.

(Examples 8 to 16 and Comparative Examples 1 to 6)

The organic EL elements of Examples 8 to 16 and Comparative Examples 1 to 6 each having a hole injection layer, a hole transporting layer, a second light emitting unit, an intermediate unit, a cavity adjusting unit, a first light emitting unit, an electron transporting layer and a cathode shown in Table 3 are used. Prepared. In the following table | surface, the number in () has shown the thickness (nm) of each layer.

As a board | substrate, the glass substrate in which the ITO (indium tin oxide) film | membrane as an anode was formed on the glass substrate was used. A hole injection layer was formed by forming a fluorocarbon (CF _x ) layer on the ITO film. (15s) in Table 3 means film formation time (seconds).

Each layer shown in Table 3 was laminated one by one by the vapor deposition method, and was formed on the hole injection layer formed as mentioned above.

The hole transport layer was formed by laminating a HAT-CN6 layer on the NPB layer.

The first light emitting unit and the second light emitting unit are white light emitting units in which a blue light emitting layer is stacked on an orange light emitting layer. An orange light emitting layer is disposed on the anode side, and a blue light emitting layer is disposed on the cathode side. In addition, in table,% is weight% unless it rejects in particular.

An orange light emitting layer and a blue light emitting layer were deposited and formed on the hole transport layer formed as described above.

The orange light emitting layer uses NPB as a hole transporting host material, TBADN as an electron transporting host material, and DBzR as a dopant material. The blue light emitting layer uses TBADN as the electron transporting host material, NPB as the hole transporting host material, and TBP as the dopant material.

On the other hand, in Example 13, Example 14, and the comparative example 5, the 1st light emitting unit and the 2nd light emitting unit are formed in a single white light emitting layer. Thus, one layer contains DBzR, an orange light emitting dopant, and TBP, a blue light emitting dopant. On the other hand, an NPB layer is formed on the anode side in the first light emitting unit and the second light emitting unit.

As the electron transporting layer of the intermediate unit, an electron transporting material can be used. In Examples and Comparative Examples shown in Table 3, BCP is used. The LUMO of BCP is -2.7 eV. The film thickness of the electron transporting layer of the intermediate unit is preferably in the range of 1 to 100 nm.

As the electron injection layer of the intermediate unit, alkali metals, alkaline earth metals and oxides thereof can be used. In Examples and Comparative Examples shown in Table 3, Li ₂ O, Li or Mg is used. The work function of Li is 2.9 eV, and the work function of Mg is 3.9 eV. In the case of metal oxides such as Li ₂ O, the work function of metals such as Li may be within the scope of the present invention. The film thickness of the electron injection layer is preferably in the range of 0.1 to 10 nm.

HAT-CN6 is used as the first electron extracting layer of the intermediate unit. The LUMO of HAT-CN6 is -4.4 eV and the HOMO is -7.0 eV. The film thickness of the first electron extracting layer is preferably in the range of 1 to 150 nm.

In Comparative Example 4, a V ₂ O ₅ layer is used in place of the first electron withdrawing layer.

NPB is used as a 1st cavity adjustment layer of a cavity adjustment unit. The LUMO of NPB is -2.6 eV and the HOMO is -5.4 eV.

HAT-CN6 is used as a 2nd electron extraction layer of a cavity adjustment unit. The film thickness of the second electron withdrawing layer is preferably in the range of 1 to 150 nm.

As an electron transport layer formed on a 1st light emitting unit, the electron transport layer which consists of a laminated structure of an Alq layer and a BCP layer is formed. On the other hand, in Examples 13 and 14 and Comparative Example 5, the electron transport layer is formed by the BCP layer alone.

On the electron transport layer it has a negative electrode comprising a layered structure of Li ₂ O layer and the Al layer is formed.

Alq is tris- (8-quinolinato) aluminum (III), and has the following structure.

[Evaluation of Organic EL Device]

For each organic EL device manufactured as described above, the driving voltage, luminous efficiency, and luminance half life were measured. The measurement results are shown in Table 4.

Here, the measurement result is a value at a drive current of 40 mA / cm 2.

As is apparent from the results shown in Table 4, in Examples 8 to 16 according to the present invention, the driving voltage is low, showing good light emission efficiency and long luminance half life.

Comparing Example 8 with a cavity adjustment unit and Comparative Example 1 without a cavity adjustment unit, Example 8 is slightly lower than Comparative Example 1 in light emission efficiency, but can be driven with the same driving voltage. The luminance half life is longer than that of Comparative Example 1. Therefore, the cavity can be adjusted by providing a cavity adjusting unit without raising the driving voltage and degrading the life characteristic.

In Comparative Example 2 in which NPB in the cavity adjusting unit was replaced with Alq, the driving voltage was significantly higher, and the luminance half life was also significantly shorter.

In addition, in Comparative Example 4 in which HAT-CN6 in the cavity adjusting unit was replaced with V ₂ O ₅ , the luminous efficiency was lowered, and the luminance half life was significantly shorter.

In addition, as apparent from the comparison between Examples 13 and 14 and Comparative Example 5, and the Examples 15 and 16 and Comparative Example 6, when the total film thickness of the NPB layer is greatly thickened, the first electron withdrawal is performed. It can be seen that the driving voltage can be reduced by inserting a plurality of HAT-CN6 layers, which are layers, at appropriate intervals.

[Organic EL display device]

6 is a cross-sectional view showing a bottom emission type organic EL display device of the embodiment according to the present invention. In this organic EL display device, light emission in each pixel is driven by using a TFT as an active element. On the other hand, a diode etc. can also be used as an active element. In addition, a color filter is provided in this organic EL display device. This organic EL display device is a back emission type display device which emits light to display below the substrate 17 as indicated by an arrow.

With reference to FIG. 6, the 1st insulating layer 38 is provided on the board | substrate 37 which consists of transparent substrates, such as glass. The first insulating layer 38 is formed of SiO ₂ , SiN _x, or the like, for example. The channel region 40 made of a polysilicon layer is formed on the first insulating layer 38. A drain electrode 41 and a source electrode 43 are formed on the channel region 40, and the gate electrode 42 is interposed between the drain electrode 41 and the source electrode 43 via a second insulating layer 39. ) Is installed. The third insulating layer 34 is provided on the gate electrode 42. The second insulating layer 39 is formed of, for example, SiN _x and SiO ₂ , and the third insulating layer 34 is formed of SiO ₂ and SiN _x .

The fourth insulating layer 35 is formed on the third insulating layer 34. The fourth insulating layer 35 is made of SiN _x , for example. The color filter layer 29 is provided in the portion of the pixel region on the fourth insulating layer 35. As the color filter layer 29, color filters, such as R (red), G (green), and B (blue), are provided. The first planarization film 36 is provided on the color filter layer 29. A through hole is formed in the first planarization film 36 above the drain electrode 41, and the hole injection electrode 38 made of ITO (indium-tin oxide) formed on the first planarization film 36 is formed. It is introduced in the through hole. The hole injection / transport unit 30 is formed on the hole injection electrode (anode) 38 in the pixel region. In portions other than the pixel region, the second planarization film 39 is formed.

The laminated light emitting unit 31 is provided on the hole injection / transport unit 30. The stacked light emitting unit 31 has a structure in which an intermediate unit and a cavity adjusting unit are provided between the first light emitting unit and the second light emitting unit according to the present invention.

The electron transport layer 32 is provided on the laminated light emitting unit 31, and the electron injection electrode (cathode) 33 is provided on the electron transport layer 32.

As described above, in the organic EL element of the present embodiment, a hole injection electrode (anode) 28 on the pixel region; Hole injection / transport unit 30; The laminated light emitting unit 31; Electron transport layer 32; And the electron injection electrode (cathode) 33 are laminated to form an organic EL element.

In the stacked light emitting unit 31 of the present embodiment, since the light emitting unit in which the orange light emitting layer and the blue light emitting layer are stacked is used, the white light emitting unit 31 emits white light. The white light is emitted through the substrate 37 to the outside, but since the color filter layer 29 is provided on the light emitting side, the color of R, G or B is emitted depending on the color of the color filter layer 29. In the case of a device emitting light in a single color, the color filter layer 29 may not be provided.

Fig. 7 is a cross-sectional view showing a top-emitting organic EL display device of the embodiment according to the present invention. The organic EL display device of this embodiment is a top emission type organic EL display device which emits and displays light above the substrate 37 as indicated by the arrow.

The part from the board | substrate 37 to the anode 38 is manufactured substantially similarly to the Example shown in FIG. However, the color filter layer 29 is not provided on the 4th insulating layer 35, but is arrange | positioned above the organic electroluminescent element. Specifically, the color filter layer 29 is attached on a transparent sealing substrate 36 made of glass or the like, and the overcoating layer 35 is coated thereon, which is formed on the anode 38 through the transparent adhesive layer 34. It adheres by adhering to. In this embodiment, the positions of the anode and the cathode are reversed from those of the embodiment shown in FIG.

As the anode 38, a transparent electrode is formed, for example, formed by laminating ITO having a thickness of about 100 nm and silver having a thickness of about 20 nm. As the cathode 33, a reflective electrode is formed, for example, a thin film of aluminum, chromium or silver having a film thickness of about 100 nm is formed. The overcoat layer 35 is formed by acrylic resin etc. about 1 micrometer in thickness. The color filter layer 29 may be of a pigment type or of a dye type. The thickness is about 1 micrometer.

The white light emitted from the laminated light emitting unit 31 is emitted through the sealing substrate 36 to the outside, but since the color filter layer 29 is provided on the light emitting side, R, G depending on the color of the color filter layer 29. Or the color of B is emitted. Since the organic EL display device of the present embodiment is a top emission type, the region in which the thin film transistor is provided can also be used as the pixel region, and the color filter layer 29 is provided in a wider range than the embodiment shown in FIG. According to this embodiment, a wider area can be used as the pixel area and the aperture ratio can be increased. In addition, since the light emitting layer having a plurality of light emitting units can be formed without considering the influence of the active matrix, the degree of freedom in design can be increased.

In the above embodiments using a glass plate as a sealing substrate, but not limited to the sealing substrate is a glass plate according to the present invention, for example, as a sealing substrate even just in the form of a nitride film such as oxide film or SiN _x, such as SiO ₂ Can be used. In this case, since a sealing substrate in the form of a film can be directly formed on the element, there is no need to provide a transparent adhesive layer.

<3rd aspect of this invention>

[Simulation result]

Table 5 sets the optical distance between the light source 101 (first light emitting layer) and the reflecting surface 103 of the reflective electrode constant in (1/4) λ as shown in FIG. 8, and the light source 102 (second light emitting layer) and The result of simulating the light emission intensity at various viewing angles when the optical distance (4/4) λ to (3/8) λ between the reflective surfaces 103 of the reflective electrode is changed is shown. The luminescence intensity was evaluated at four viewing angles of front (0 °), 30 °, 45 ° and 60 °. On the other hand, Table 5 shows the relative values of the emission intensity in the front direction as 1. "Maximum / Min" represents the ratio of the maximum and minimum in these four viewing angles. "Front intensity" shows a relative intensity in which the light emission intensity in the front direction when the light emitting layer is the first light emitting layer alone is 1.

In Table 5, (2), (4), (6) satisfied the conditions of this invention.

As shown in Table 5, in (2), (4), and (6) satisfying the conditions of the present invention, relatively high light emission intensity was obtained at any viewing angle of 30 °, 45 °, and 60 °, and the maximum / minimum value was obtained. The ratio of is smaller than the other. Thus, it can be seen that the viewing angle dependency is reduced.

As is clear from Table 5, when only the first light emitting layer is provided, the light emission intensity is the lowest at the viewing angle of 60 degrees. Therefore, the viewing angle dependency can be reduced by setting the second light emitting layer to have a high light emission intensity at 60 °.

Optical distance is calculated | required by the film thickness and refractive index of each layer, and also considering multi mode, in this specification, it calculated by simplifying the refractive index and multi mode of each layer.

(Example 17)

9 is a schematic cross-sectional view showing the organic EL device manufactured in this embodiment. In the organic EL device of this embodiment, as shown in Fig. 9, a metal thin film 81 made of Al is formed on a substrate (not shown), and a transparent conductive film 82 made of an ITO (indium tin oxide) film thereon (film Thickness of 30 nm) is formed. The reflective electrode is comprised by this transparent conductive film 82 and the metal thin film 81, and the upper end surface of the metal thin film 81 becomes the reflecting surface 41a.

On the transparent conductive film 82, a hole transport layer 91 (film thickness of 30 nm) made of NPB is formed. This hole transport layer 91 also functions as a first cavity adjustment layer.

On the hole transport layer 91, an orange light emitting layer 51 (film thickness 60 nm) and a blue light emitting layer 52 (film thickness 50 nm) are laminated in this order. The orange light emitting layer 51 and the blue light emitting layer 52 constitute a first light emitting layer 50 of white light emission. The light emitting position 50a of the first light emitting layer 50 is a region 5 nm away from the interface between the orange light emitting layer 51 and the blue light emitting layer 52 toward the blue light emitting layer.

The orange light emitting layer 51 is formed by using NPB, which is a hole transporting material, as a host material, 100% by weight, and using DBzR, which is an orange light emitting dopant, to 3% by weight.

The blue light emitting layer 52 is formed by using 100% by weight of TBADN, which is an electron transporting material, as a host material, and containing 1% by weight of TBP, which is a blue light emitting dopant.

On the first light emitting layer 50, the electron transport layer 71 (film thickness 20 nm), the electron injection layer 72 (film thickness 10 nm), and the electron extraction layer 73 (film thickness 20 nm) are laminated in this order. It is. The intermediate unit 70 is composed of an electron transport layer 71, an electron injection layer 72, and an electron extraction layer 73. The electron transport layer 71 is made of Alq. The electron injection layer 72 is formed by depositing Li, but since the film thickness is very thin, it is considered that the electron injection layer 72 has a composition of Alq: Li = 1: 1, which is a composite with Alq of the electron transport layer 71. The electron extraction layer 73 is made of HAT-CN6.

The second cavity adjustment layer 92 (film thickness 275 nm) is formed on the intermediate unit 70. The second cavity adjustment layer 92 is also formed of NPB.

On the second cavity adjustment layer 92, an orange light emitting layer 61 and a blue light emitting layer 62 are stacked in this order. The second light emitting layer 60 is composed of an orange light emitting layer 61 and a blue light emitting layer 62. The orange light emitting layer 61 and the blue light emitting layer 62 are formed in the same manner as the orange light emitting layer 51 and the blue light emitting layer 52 of the first light emitting layer 50.

The light emission position 60a of the second light emitting layer 60 is a region 5 nm away from the interface between the orange light emitting layer 61 and the blue light emitting layer 62 on the blue light emitting layer 62 side.

An electron transport layer 93 (film thickness of 20 nm) is formed on the second light emitting layer 60. The electron transport layer 93 is made of Alq.

On the electron transport layer 93, a metal thin film electrode 94 (Li film thickness of 1 nm: Ag film thickness of 15 nm) made of Li / Ag as a light extraction side electrode is formed.

By adjusting the film thickness of the first cavity adjustment layer 91, the optical distance between the light emitting position of the first light emitting layer and the reflecting surface of the reflecting electrode and the optical distance between the light emitting position of the second light emitting layer and the reflecting surface of the reflecting electrode can be adjusted. have. In addition, by adjusting the film thickness of the cavity adjustment layer 92, the optical distance between the light emitting position of the second light emitting layer and the reflecting surface of the reflective electrode can be adjusted.

In the organic EL element configured as described above, the optical distance between the light emitting position 50a of the first light emitting layer 50 and the reflecting surface 91a of the reflecting electrode is 125 nm. The optical distance between the light emitting position 60a of the second light emitting layer 60 and the reflecting surface 81a of the reflecting electrode 80 is 312.5 nm.

The first light emitting layer 50 and the second light emitting layer 60 in this embodiment are white light emitting layers laminated with an orange light emitting layer and a blue light emitting layer, and the central wavelength λ of the light to be extracted is 500 nm. Therefore, the optical distance between the light emitting position of the first light emitting layer and the reflective surface of the reflective electrode is (1/4) λ, and the optical distance between the light emitting position of the second light emitting layer and the reflective surface of the reflective electrode is (5/8) λ It is. Therefore, it is set to fall within the scope of the present invention.

It is a figure which shows the emission spectrum in the front direction of the organic electroluminescent element shown in FIG. 9, and the emission spectrum in the viewing angle 60 degree direction. As shown in FIG. 10, it can be seen that the light emission intensity in the front direction and the light emission intensity in the viewing angle 60 ° are almost the same, and the viewing angle dependence is reduced. When the light emission intensity in the front direction at the wavelength of 500 nm is 100, the light emission intensity in the viewing angle of 60 ° is 83.

(Comparative Example 7)

11 is a schematic cross-sectional view showing the structure of an organic EL device of Comparative Example 7. FIG. As in the seventeenth embodiment, a metal thin film 41 is formed on a substrate, and a transparent conductive film 42 is formed on the metal thin film 41. The hole transport layer 51 is formed on the transparent conductive film 42. The orange light emitting layer 11 and the blue light emitting layer 12 are formed on the hole transport layer 51. The electron transport layer 53 is formed on the blue light emitting layer 12. On the electron transport layer 53, a metal thin film 54 made of Ag as a light extraction electrode is formed.

In the organic EL device of Comparative Example 7, only one light emitting layer is provided, and only the first light emitting layer 10 is provided. The optical distance between the light emitting position 10a of the first light emitting layer 10 and the reflecting surface 41a of the reflecting electrode 40 is 125 nm.

It is a figure which shows the emission spectrum in the front direction of the comparative example 7, and the emission spectrum in the viewing angle 60 degree direction. As is apparent from FIG. 12, there is a big difference between the light emission intensity in the front direction and the light emission intensity in the viewing angle of 60 °. For example, at a wavelength of 500 nm, the light emission intensity in the viewing angle 60 ° direction is 68 with respect to the light emission intensity 100 in the front direction, indicating that the viewing angle dependence is large.

(Comparative Example 8)

In the structure similar to Example 17 shown in FIG. 9, the organic electroluminescent element which manufactured the distance between the light emission position 20a of the 2nd light emitting layer 20, and the reflecting surface 41a of the reflection electrode 40 to 375 nm was manufactured. . 375 nm is equivalent to (3/4) lambda when the wavelength lambda = 500 nm.

When the light emission intensity in the front direction at the wavelength of 500 nm of the comparative example 8 is 100, the light emission intensity in the viewing angle 60 ° direction is 64. Therefore, it can be seen that the viewing angle dependence is greater than that of the seventeenth embodiment.

As is apparent from the above, the organic EL device of Example 17 designed according to the present invention can greatly reduce the viewing angle dependence compared to the organic EL devices of Comparative Example 7 and Comparative Example 8.

According to the present invention, the cavity can be easily adjusted without changing the film thickness in each light emitting unit, and the cavity can be adjusted while having high luminous efficiency, reducing the driving voltage, increasing the reliability, and reducing the viewing angle dependency. It is possible to provide an organic EL device which can be used and an organic EL display device using the same.

Claims (22)

delete delete cathode; anode; An intermediate unit disposed between the cathode and the anode; A first light emitting unit disposed between the cathode and the intermediate unit; A second light emitting unit disposed between the anode and the intermediate unit; And a cavity adjusting unit disposed between the intermediate unit and the second light emitting unit and installed adjacent to the intermediate unit, The intermediate unit has a first electron withdrawing layer for drawing electrons from the cavity adjusting unit, and an electron injection layer adjacent to an anode side of the first electron withdrawing layer, The cavity adjusting unit is provided adjacent to the cathode side of the first electron withdrawing layer, and withdraws electrons from the first cavity adjustment layer for withdrawing electrons to the first electron withdrawing layer and the electron supply layer adjacent to the cathode side. Having a second electron withdrawing layer for Absolute value of energy level of lowest covalent orbital LUM0 of the first electron withdrawing layer LUMO (B) and absolute value of energy level of highest point molecular orbital HOMO of first cavity adjusting layer HOMO (A) || | || |||||||-| The relationship of HOMO (A) |-| LUMO (B) | <1.5eV, and the absolute value of the energy level of the lowest covalent orbital LUM0 of the said electron injection layer | Absolute value | WF (C) | is smaller than | LUMO (B) | Absolute value | LUMO (D) | of energy level of lowest co-molecular orbital (LUMO) of the said 2nd electron fetching layer | HOMO (E) | | HOMO (E) |-| LUMO (D) | The absolute value of the energy level of the lowest covalent orbital (LUMO) of the said 1st cavity adjusting layer, and has the relationship of ≤1.5eV | LUMO (A) | and | LUMO ( D) | The organic electroluminescent element characterized by having a relationship of | LUMO (A) | <| LUMO (D) | The organic electroluminescent device according to claim 3, wherein the electron supply layer is provided in the first light emitting unit. The organic electroluminescent device according to claim 3, wherein the electron supply layer is a second cavity adjustment layer provided in the cavity adjustment unit. The organic electroluminescent device according to any one of claims 3 to 5, wherein the cavity adjusting layer is formed of a hole transporting material. The organic electroluminescent device according to claim 6, wherein the hole transporting material is a tertiary arylamine-based material. The organic electroluminescent device according to claim 3, wherein the cavity adjusting unit includes the first cavity adjusting layer and the second electron extracting layer in a plurality of repeating units. The absolute value of the energy level of the lowest co-molecular orbital LUM0 of the electron transport layer, and the electron transport layer is provided between the electron injection layer and the second light emitting unit in the intermediate unit. An organic electroluminescent device, wherein | I is less than | LUM0 (C) | or | WF (C) |. The organic electroluminescent device according to any one of claims 3 to 5, wherein the electron extracting layer is formed of a pyrazine derivative represented by the structural formula shown below. &Lt; Formula 1 >

(Wherein Ar represents an aryl group, R represents hydrogen, an alkyl group having 1 to 10 carbon atoms, an alkyloxy group, a dialkylamine group, or F, Cl, Br, I or CN) The organic electroluminescent device according to claim 10, wherein the first and / or second electron withdrawing layer is formed of a hexaazatriphenylene derivative represented by the structural formula shown below. <Formula 2>

(Wherein R represents hydrogen, an alkyl group having 1 to 10 carbon atoms, an alkyloxy group, a dialkylamine group, or F, Cl, Br, I or CN) Reflective electrodes; A light extraction side electrode; And a first light emitting layer and a second light emitting layer disposed between the reflective electrode and the light extraction side electrode, The optical distance between the light emitting position of the first light emitting layer and the reflecting surface of the reflective electrode is (n / x) λ, and the optical distance between the light emitting position of the second light emitting layer and the reflecting surface of the reflective electrode is [(n + m) / 2x Λ (λ is the center wavelength of light emission to be extracted, n is odd, m is even, x is a natural number), and the first light emitting layer and the second light emitting layer are laminated through an intermediate unit, and the first light emitting layer and An organic electroluminescent device, characterized in that the white light emitting layer having a structure in which each of the second light emitting layers is laminated. delete 13. The method of claim 12, wherein the first light emitting layer is disposed between the reflective electrode and the intermediate unit, and the second light emitting layer is disposed between the light extraction side electrode and the intermediate unit. A first cavity adjusting layer is provided between the first light emitting layer, and a second cavity adjusting layer is provided between the intermediate unit and the second light emitting layer. The method according to claim 12 or 14, wherein One of the reflective electrode and the light extraction side electrode is an anode, and the other is a cathode; An electron withdrawing layer in which the intermediate unit is provided on the cathode side; An electron injection layer adjacent to an anode side of the electron extraction layer; And an electron transport layer adjacent to the anode side of the electron injection layer, The electron extracting layer extracts electrons from an adjacent layer adjacent to the anode side, and supplies the extracted electrons to the anode side through the electron injection layer and the electron transporting layer, and at the same time, the electron extracting layer is generated in the adjacent layer by extraction of electrons. The hole is supplied to the cathode side, the organic electroluminescent element. The organic electroluminescent device according to claim 14, wherein the first cavity adjustment layer and / or the second cavity adjustment layer is formed of a hole transporting material. The organic electroluminescent device according to claim 12 or 14, wherein the white light emitting layer has a structure in which an orange light emitting layer and a blue light emitting layer are stacked. An organic electroluminescent element having an element structure sandwiched between an anode and a cathode, and an active matrix driving substrate provided with an active element for supplying a display signal corresponding to each display pixel to the organic electroluminescent element, wherein the organic electroluminescent element Is a bottom emission type organic electroluminescent display device having a light emitting electrode disposed on the active matrix driving substrate and having an electrode provided on the substrate side of the cathode and the anode as a transparent electrode. An organic electroluminescent display device comprising the organic electroluminescent element according to any one of claims 3 to 5, 12 and 14 as the organic electroluminescent element. The organic electroluminescent display device according to claim 18, wherein the organic electroluminescent element is a white light emitting element, and a color filter is disposed between the organic electroluminescent element and the substrate. An organic electroluminescent element having an element structure sandwiched by an anode and a cathode; An active matrix driving substrate provided with an active element for supplying a display signal corresponding to each display pixel to the organic electroluminescent element; And a transparent sealing substrate provided opposite the active matrix driving substrate, wherein the organic electroluminescent element is disposed between the active matrix driving substrate and the sealing substrate, and is provided on the sealing substrate side of the cathode and the anode. An organic light emitting display device having a top emission type using an electrode as a transparent electrode. An organic electroluminescent display device comprising the organic electroluminescent element according to any one of claims 3 to 5, 12 and 14 as the organic electroluminescent element. The organic electroluminescent display device according to claim 20, wherein the organic electroluminescent element is a white light emitting element, and a color filter is disposed between the organic electroluminescent element and the sealing substrate. The organic electroluminescent device as described in any one of Claims 3-5, 12, and 14 is used.

Images